System of radiocommunication



2 Sheets-Sheet 1 INVENTOR [ma/yleana//e E. L. CHAFFEE SYSTEM 0F RADIO COMMUNICATION Filed .1mg4 11, 1922 sept. 13, 1927.

A TTRNEY Se t. 13 1927. '1"'79115H- 'p' 22 E. 1.. CHAFFEE SYSTEM OF RADIO COMMUNICATION '2- Shee'ts-Sheet 2 Filed Aug.. 11, 1922 QAWU INVENTOR. 2571054/ am (n/? BY Q l g ATTovRA/YA Patented Sep-t. 13, 1927..

.UNITED-STATES 1,642,663 PATENT orifice.

Eamonn LEON cnnrrnn, or BELMONT, MAssAoHn'snTTs, AsSIeNon To JOHN HAYs HAMMOND, Jn., or eLoqcnsTnn, MASSACHUSETTS.

-. SYSTEM 0F BAIIOCOMM'UINICATION.

Application nled August 11, 1922. serial` No. 581,280.

This invention relates fto the transmission of intelligence by radiant energy,and more 'particularly to systems for secret radio telephony y An obj ect of' this invention is to provide a system comprising a sending station arranged to emit.` radiant energy of a peculiar character, and a coordinating receiving station provided with apparatus res vonsive to energy having the peculiarities o the emitted energy. l v

A further object o'fthe invention is to pro; vide a simple arrangement for the'emission of radiant energy in the form of oscillations havingl a fundamental frequency which may be wbble'd, said oscillations being modulated at one or more lower supersonic frequencies,

and each of said supersonic frequencies being 'made effective by signals, such for ex?- ample, as voice waves, and being modulated 'by them, and to arrange for the selective rec ception of such energy and its transformation into sensible manifestations. I

' Still other objects of the invention will appear from the following description taken in connection' with the drawings which form a lart of this agpplication and in which,

i ."1 is a'. iagramofasending station whic is -an embodiment of this invention, and

Fig. 2 isa diagram of a receivin station arranged to cooperate withthe sen ing station of Fig. 1.

I as is well known in the art, but according to' A an ordinary receiver..x

' 6 The system shown inthe drawings employs at its sending station a carrier Wave of relatively high frequency upon which there is "impresse -onelor more series of amplitude variations' of relatively lower butsupersonic frequency which. are made effective by speech 'or Aother desired'signals and are modulated thereby. The mbdulation 'of the lower Supersonic frequency produces side bands,

the present invention, oneof these, side bands ris suppressed.A Furthermore, the carrier wave may be wohbled in fre uency inv an erratic manner, .and is :modu wated -by the modulated alower,` Supersonic frequency only- "when signals are impressedso that there is emitted from the sending station, radiant. energy of a character which will not actuate In a general way, the receiving Set may be described as comprismg two or more resonant circuits arranged in series, one tuned to the carrierA fre uency mentioned` above, and the otheror ot erstuned to the modulated lower, Supersonic frequency or frequencies,

or each impinge, 'and a, grid 13 for controlling the passage of electrons. lThese parts are con,

nected 'with' inter-related, -inductivelyfcoupled circuits in Such a manner that the energy inthe plate circuit reacts on the grid circuity so-as to cause the deviceto oscillate regeneratively. There is thus produced an 'oscillatory current of a relatively high frequency, determined by the electrical` constants "of the inter-related circuits.

For producing oscillations of relatively lower but supersonic frequency, a second thermionic tube 20 having the usual filament 11:, plate 12 and grid 13, isconnected in a regenerative circuit arrangement comprising a transformer having windings 22 and 23,=which are included in.the plateand grid circuits respectively. This 'transformer also comprises a third winding 24 connected in the input circuit of a m'odulator which will be hereinafter described. The plate 12 is y maintained at a positive potential with res ect to the filament 11 by a usual B battery 2g whose positive terminal is connected through aninductance 28 to the'plate. Thi regenerative circuit arran ement is rovide with suitable condensers 2g and 26,t e capacity of which may be adjusted to cause oscillations of a upredetermined frequency, relatively lower than those of the master "oscillator 10, t0 be producedby the generator 20. v

For `transforming or steppingv up voice or othersignal currents into a frequency range of relatively high or supersonic freare produced inthe series with a tele hone transmitter' 32 and its secondary windings respectively connected in the input circuits of a air of'thermionic devices 33 and 34, eac comprising a customary filament, output circuit of the t ermionic devices 33 and 34 includes the primary windings of a coupling transformer 35, the secondary winding of which isfconnectepl to a hand filter 36 adapted for either highass or lowpass filtration. The windings o transformers 31 and 35 are so connected that theelectromotive forces in the filter 3,6 are equal and o posite when' no signal is being impresse onA the transmitter 32. Consequent- 1y, the lower, supersonic frequency is suppressed except when the transmitter 32 is producing current variations. As shown, the devices 33 and 34 are arranged in th form of a so-called push pull modulator, by means of' which electro-motive forces corresponding to the two side bands of the voice modulated lower supersonic frequency filter 36. The filter comprises any suitable combination of in- Aductances and capacities such 'as to permit' the'passage ofpne only ofthe side bands resulting from modulation of' the lower supersonic frequency by the signal. It is preferable to employ a band filter arranged yto permit the flow of the lower band and to suppress all other currents including the upper band.

For example,lassuming the lower, super-y sonic frequency to be 40,000 cycles per second.. and. assuming that voice currents including frequencies ranging from 200 to 2000 cycles per secondare used for signals, two side bands will be produced in the outut circuit of the modulator 33, 34, one

rom 39,800 to 38,000 cycles inclusive. and the .other from 40,200 to 42,000 cycles in.- clusive. Thefilter 36 will suppress the u per side band and there will, therefore, e transmitted b the filter a band of frequen- :cies ranging rom 39,800 to 38,000 inclusive.

heftoutput circuit of the filter 36 is connected to the primary Winding of a coupling transformer 40.. the secondary winding of which is included in` the grid circuit of a second side band modulator. This side band modulator comprises a thermionic device 41 including the usual filament, grid and plate. The internal plate-filament circuit o f thethermionic device 41 is connected in series with aninductance 42 and in shunt .with a windingv 43 of a coupling,r transformer 44. The winding 43 isincluded in the output circuit of the master oscillator andthe secondary winding 45 of the transformer 44 is included in the .circuit of the antenna 46 in such manner that energy supplied by the master 'oscillator 10 is varibly `withdrawn from the antenna circuit b upon the operation of the device 41.

late and grid. The

'. waves.

consists The antenna circuit which includes the winding 45 of the coupling transformer 44 may include also a so-called wobbler 50 for varying in anerratic manner the frequency of the oscillations emitted by the antenna. The wobbler includes a pair of contacts 51 and 52 intermittently closing at .different rates the circuits of a corresponding' pair of condeiisers 53 and 54,; and also comprises a rotatable vane 55, passing intermittently adjacent to a stationary segment 56, whereby the capacity betweenthe vane and the segment is intermittently varied at a relatively high rate. The vane and segment thus constitute a variable capacity and in lcombination with the variations in capacity caused by the intermittent closures'of the contacts 51 and l52, produce rapid and erratic changes in the electrical characteristics of the circuit of the antenna and the winding 45 of the transformer 44. `Thus the electrical constants of the antenna circuit and the frequency of the oscillations 1nduced thereinare rapidly changed in a manner determined by the varying combinations set up by the wobbler mechanism 50.

The circuits of one form of receivin station 'embodying the invention are s own in Fig. 2. These comprise a receiving element positioned so as to intercept Hertzian As shown, this receiving element of an antenna 60, which includes ,an inductance 61 coupled to a closed oscilatory circuit 62, comprising an inductance 63 and a variable condenser 64. The inductance 61 is also variably coupled with an inductance 65. The closed oscillatory circuit 62 is connected in theninput circuit of a thermionic device 66 having the usual 'filament 11 for emittingelectrons, a plate 12 upon which the electrons impinge, and a grid 13 for controlling the. passage of elec- The filament 11 of 'the thermionic device 66 may be heated by current supplied by al battery 70 and controlled by a variable resistance 71. In shunt with the filament 11 is a potentiometer 72 having ay slider 73 connected with the closed, oscillatory cir# cuit 62 whereby the normal potential maintained upon the grid 13, relative tov the. lila.-

ment l1. may be adjusted. The output cirinductance 65 and the primary winding of an intervalve transformer 74. This primary winding is designated by 75 and has aby-pass condenser 76 in shunt therewith.

The other end of the winding 75 is concuit of the therniionic device 66 includes the between these circuits comprises a transformer 81, one winding of which is shunt- `ed .by a variable condenser 82 by means of which 4the oscillations generated may be made of the same frequency as the currents produced bythe lgenerator at the sending station. The Aoutput circuit l of the oscillator 8O includes the closed, os-

y cillatory circuit formed by awinding of the transformer 81 and the variable condenser ,82 and also the primary winding of a. trans,-

former-83. The other end of the primary j -Winding of the transformer 83 is connected to the positive terminal of the plate potential source 77 `whereby the plate'of the ther- "mionic device 80 is maintained at a positive potential relative to the filament.

A potentiometer 90 'is connected across the tilamentheating battery 70, and includes a slider 91 connected to the secondary winding 78 of the transformer 74, and a variable condenser 92 formswith thiswinding 78 a closed, oscillatoryl circuit, the other end of which is connected through the secondary winding of the transformer 83 with the input circuit of a thermionic device 100; The oscillator 80, 81, 82 in combination with the transformer 83 forms a homodyne for impressing upon the input circuit of the thernuonic device 100 an oscillatory electro-motive force corresponding in frequency to that of the suppressed currents produced by the generator 20 at the sending station.

The output circuit of the thermionic device 100 is'connected to an indicating device, which, as s hown is a telephone receiver r 101 provided w1th a by-pass condenser 102.

`rI his output circuit also includes alconnection between the indicating device and the positive terminal ofthe potential source 77.

When the transmitting st tion is actuated and radiant energy emittedejtherefrom of the composite character hereinbefore described, the operation ofthe receiving system isias follows. The radiant energy, 'intercepted bv the circuit which includes the antenna 60. induces oscillations in the closed. oscillatory circuit 62, which is tuned to be responsive to the radiated energy of the sending station. The slider 73 is so adjusted that the thermionic device 66v operates on a curved portion of its .characteristic curve u nd thus the device 66 acts to detect or rectify 'these oscillations. Its output circuit transmits these rectified oscillations through .the inductance which is adjustably coupled with the-inductance 61 so that these transmitted oscillations are regeneratively amplified.

The superimposed current flowing 1n this .output circuit varies in amplitude accordingto the modulations impressed upon the carrier Wave at the-sendm statlon, and there j appears in the circuit o the primary winding 7 5 of the inter-valve transformer 74:, an

.uni-directional current having the frequen cies, and characteristics of the unsuppressed side band of the modulated lower, supersonic frequency of the sending station. The closed, oscillatory circuit 78, 92 is tuned tothese frequencies byadjusting thecondenser 92.

It has been shownthat the thermionic device 80 with its connected circuits forms a homodyne which impresses uponthe input circuit of the thermionic device 100 an oscillatoryl electro-motive force corresponding in frequencyl to that of the suppressed currents produced by the generator 20 at the sending station, an'd it may now be seen that this electro-motive force -is ycombined with the oscillations induced in the closed oscil latory circuit 78, 92.

The slider 91 ofthe potentiometer 90 is so adjusted that the thermionic device 100 operates on a curved portion of its charac teristic curve to cause it to detect or rectify these'combined oscillations impressed upon its input circuit. Thusthere'are produced in the output circuit of the thermionic device 100 `currents varying in amplitude in accordance with the signal currents. These currents cause the telephone 101 to produce sound waves of the same character as those which operated the signal transmitter 32.

Wren the signal transmitter 32 is not being ctuated currents of the lower, supersonic frequency oppose and neutralize each other so that they have no effect upon the energy radiated from the sending station. Since the homodyne at the receivingr station produces oscillations at a frequency above ,the range of audibilityfor the ordinary oproduce audible signals evi'ce 101 under these are modulated. Furthermore, Wl en lthe wobbling mechanism is employed t e emitlted energy is further distorted'.A

lia

" made without departing from the spirit of- `means interposed between the generators for ample, a number ower frequency than that of the master oscillator, maybe employed so that a correspondin plurality of speech or other sign als may` e transmitted and received at one i time.'

vAnother mpdication, which may be the invention, is to employ the system' for telegrafgiic signals or radio-dynamic control. v the latter case, thev signal modulated -frequency referred to above as the supersomc frequency may lbe below the upper limitof audibility, but above the rate at which the desired signals are transmitted. I intend no limitations other than those im osed by the following claims. at is claimed is: 1. Apparatus for emitting radiant energy comprising va generator of high frequency oscillations, another kand independent ge erator of oscillations of lower frequency,

A producing in said high frequency oscillations amplitude .variations of frequencies differin g from said lower frequency inl accordance with signals, and means for wobbling the frequency `of the `high frequency oscillations. 2. -Apparatus for emitting radiant energy y comprising a generator of high frequency y oscillations, means including another generator ofoscillations of different frequency f or producing in said high frequency oscillations amplitude variations of supersonic frequencies;varying` in accordance with telephomc signals, and means for wobbling the requency of the high frequency oscillations.

i A radio system comprisin a sending station having a generator of hi frequency oscillations, means for producing periodic variations of said high frequency oscillations of a lfrequency lower than the frequency of said oscillations but aboveaudibility, said means being arranged to be non-actuative when not affected by signals, a telephonev transmitter arranged when operated to cause said variation producing means to affect the high frequency (oscillations, whereby waves modified by telephonically-controlled, periodic variations are .produced and means for wobbling the high equenc oscillations, and aJ receiving arrangement aving an .ele-

This would make itpstilly more \dif. an 4unauthorized station to dis-n of supersonic frequencies ment arran ed to intercept said waves, a closed, oscilitory circuit responsive tothe high frequency oscillations, another closed, oscillatory circuit timed to the signal-controlled, periodic variations, und means `for ti'aiisforiiiing the energy set upin said circuits into sensible manifestations.'

4. A radio system comprising a sending station having a generator of high frequencyoscillations and meanfs for impressing sig-" nal-controlled periodic variations upon said high frequencyoscillations, said means in-v cluding another generator of oscillations of different frequency, 'a push-pull modulator interposed between said generators,a signal 80' transmitter cooperatively associated with the modulator and means for wobbling the high frequency oscillations andareceiving arrangement having an element arranged to intercept said waves, a closed, oscillatory circuit responsive to the high frequency os, cillations, another closed, oscillatory circuit tuned tothe signal-controlled periodic vari,- ations and means for transforming the env err set u in said circuits into sensible maii- 9" s P y ifestatiens. 5. Apparatus for emitting radiant energyconiprising a generator of high frequency Q S- cillations, means for stepping up voicefclurrents into a supersonic frequency range re-- taining the characteristics of the voice cur-' rents, means for producing amplitude varil ations in the currents generated bv the high; frequency generator according to the stepped up supersonic voicel currents and means for wobbling the frequency of the high' frequency oscillations, 6. A radio system comprising a sending station having a generator of high frequenv cy oscillations, means for transforming signal currents into a supersonic frequency range retainingv the characteristicsof the l signalI currents, means for modulating the currents generated by the high 'frequency generatoraccording to the transformed supersonic signal currents, whereby waves of said high frequency modified bysignal-con-l trolled, supersonic'variations are produced. and means for wobbling the frequency .of the high frequency oscillations and a receiv- `ing arrangement having elements tunedto the high frequency oscillations and the s1gnal-controlled periodic variations respectively and means fortransforming the eiiergy set up in said elements into sensibleV 12" manifestations. l 7. A ra'dio system `comprising a sending station having a generator'of high frequency oscillations, means for transforming signal currents intoa supersonic frequency range retaining the characteristics of the signal currents, means for producing amplitude variations in the currents generated by. .the high frequency generator according to the transformed supersonic signal currents, 130

'quenc oscillations and the signal-controlled perio ic 'variations respectively, a vacuum tube detector interposed between said circuits, and means for transforming the energy set up in said circuits into energy of audible frequency having the characteristics of the signal currrents. y

8. A radio system comprising a sending station having a generator of high fretransformed quency oscillations, means for impressing upon the ether waves derived from said oscillations, means for transforming voice cur- ,rents into a supersonic frequency range `retaining the characteristics of the voice currents, means for modulating the oscillations produced by the generator according to the supersonic voice whereby Waves of said high frequency modified by voice-controlled periodic variations are produced, and means for wobbling the frequency of said high frequency oscillations and -a receiving arrangement having an lelementuarranged to intercept said waves,

circuits reson-antly fresponsive to the high frequency oscillations and to current of the frequency of the voice-controlled periodic variations respectively, and m'eans'for transwhich consists of transforming signal cur-l 'forming the energy set up in said circuits into sensible manifestations.

9. A method of transmitting radio signals rents 'into a relatively high frequency range, utilizing said highl frequency currents to modulate currents of still higher frequeney,l

wobbling the frequency of the last mentioned currentsrec-iving the waves thus produced, transforming the received energy to the first-named frequency range by simple. detection without the use i of a local source of energy, detecting the transformed energy, and actuating an indicating device thereby.

10. A radio system comprisinga sending station having a generator of high frequency oscillations, another generator of oscillations of different frequency, a push-pull modulator interposed betweenV said generators, means interposed between the modulator and the generator of high frequency oscillations for producing amplitude variations in the high frequency oscilaltions in accordance .with a side band produced by the modulator from said oscillations of different frequency,

' and a wobbler for varying erratically the frequency of the high frequency oscillations, and a receiving arrangement having an element positioned to intercept Waves from the sending station, a closed, oscillatory circuit responsive to said high frequency oscillations, another closed, oscillatory circuit recurrents,

vsponsive to said amplitude variations-and `means for transforming the energy set up erated to produce sidecbands from said os- 4 cillations of different frequency, means for suppressing one lofsaid side bands, :means interposed between said suppressing means 'and the generator o f high frequency oscillations for modulatin the high frequency oscillations in accordance with the unsuppressed side band, and a wobbler for varying erratically the frequency of the energy produced by the sending station and a receiving arrangement having an element ar- -ranged yto intercept said waves, a closed, oscillatory circuit responsive tosaid high frequency oscillations, another'closcd, oscillatory circuit resonant to the signal-controlled modulations produced in the high frequency oscillations, a generator of oscilations coi-rcsponding with the oscillations of said different frequency associated with said other closed, oscillatory circuit, and means for transforming the energy set up in said cir- Acuits into sensible manifestations.

12. A radio system comprising a sending station having a generator of high frequency oscillations, another generator of oscillations of a 'different frequency, a. lpushpull modulator interposed between sait generators, a signal transmitter arranged when operated to produce side bands from said oscillations of different frequency, means for suppressing the higher of said side bands, means interposed between said suppressing means and the generator of high frequency oscillations for producing amplitude variations in the high frequency oscillations in accordance with the unsupi tions corresponding with the oscillations of said different frequency associated with said other closed oscillatory circuit, and means for transforming the energy set up in said circuits into sensible manifestations.

13. A radio system comprising a sending station having a generator of high frequency oscillations, another generator ofescillations of a lower frequency, a modulator interposed between said generators, a signal transmitter arranged when operated to produce side bands from said oscillations gf lower frequency, means for suppressing one of said side bands, means inter osed between said suppressing means an the generator of hilgh frequency oscillations for modulating t e high frequency oscillations in accordance with thev unsuppressed side band, and\a wobbler for varying the frequency of the high frequency oscillations and a receiving arrangement having a tuned circuit responsive to said high frequency oscillations, another tuned circuit responsive to the signal-controlled modulations produced .inl the high frequency oscillations a generator of oscillations corresponding with i the oscillations of said different frequency mani estations.

- erator of high t circuits res ectivel associated with said other closed, oscillatory circuit, and means for transforming the energ set up in'said circuits into sensible 14. Apparatus for emitting radiant eneigy' comprising a three-electrode tube genrequency oscillations includiii its input and output an oscillator coupled wit `said rst-mentioned circuits so ing windings 'as mainlyv to determine the frequency of the circuit A produced by the generator, said oscillatory circuit for wobforl emitting radiant `energy comprising a three-electrode tubel generator of high frequency oscillations including windings in its input and4 output circuits respectivel an antenna containing a Winding coupled; to said first-mentioned windings, a closed scillator circuit including said last-mentioned Win ing andV mainly determining the frequency of the oscillations produced by the generator, means in said oscillatory circuit for Wobbling the fre` quency of the high frequency oscillations and means for modulating said oscillations comprising a three-electrode tube having its plate filament circuit connected in parallel With the erating tu In testimony whereof I hereunto affix my signature. E. LEON CHAFFEE.

frequency of the hio'h frequencye Elate filament circuit ofthe gen- 

